Abstract:

Astrophysical evidence on a variety of distance scales clearly shows that we cannot account for a large fraction of the mass of the universe. This matter is “dark”, not emitting or absorbing any electromagnetic radiation. A compelling explanation for this missing mass is the existence of Weakly Interacting Massive Particles (WIMPs).These particles are well motivated by particle physics theories beyond the Standard Model, and the discovery of WIMPs would have enormous impact on both astrophysics and particle physics. WIMPs, if they exist, would occasionally interact with normal matter. With a mass in the GeV to TeV range, and moving at speeds relative to the Earth of hundreds of kilometers per second, WIMPs would deposit energies in the tens of keV when elastically scattering with nuclei. Detectors that are low in radioactivity and sensitive to small energy depositions can search for the rare nuclear recoil events predicted by WIMP models. In recent years, several new efforts on direct dark matter detection have begun in which the detection material is a liquefied noble gas. Advantages include: large nuclear recoil signals in both scintillation and ionization channels, good scalability to large target masses, effective discrimination against gamma ray backgrounds, easy purification, and reasonable cost. I will discuss the advantages and disadvantages of the various noble gases. I will also describe some current efforts in the field, notably the LUX and LZ experiments which use liquid xenon as a target material, and the possible use of liquid helium for low-mass dark matter detection.